The present invention relates to a web rewinder for unwinding parent rolls of web material such as, for example, paper, and rewinding the web onto cores to produce consumer rolls of web product such as rolls of paper towels, or rolls of toilet tissue. More specifically, the present invention relates to a web chop-off and transfer mechanism providing improved reliability for such web rewinder.
Rewinders are apparatus for unwinding parent rolls of web material such as paper and rewinding the web into consumer product rolls. Such product rolls include paper towels and toilet tissue each of which typically comprise multiple tear-apart sheets. Rewinders may include a perforating cylinder for making traverse lines of perforations in the web at sheet length intervals providing lines of weakening for tear apart convenience. The reminders often include a rotating turret assembly supporting a plurality of mandrels which in turn support the cores on which the product is wound in order to produce consumer product rolls. The rotating turret assembly provides a mechanical means for core loading, core gluing, web rewinding, and log stripping. The transfer of the web from a fully wound core to an empty core is performed by a web transfer and web chop-off mechanism.
For conventional turret winders, the web chop-off occurs at a position between adjacent mandrels. The turret winder may be equipped with a plurality, typically six or more mandrels, each of which goes through the same orbital path. This permits the mandrel to be equipped with a paperboard core on which the tissue or toweling is wound, the core faced with glue, the actual winding, and ultimately the removal of the wound roll from the mandrel. Near the end of the rewinding on a given mandrel core, the subsequent mandrel is in a position close to the fast traveling web so as to pick it up and continue the rewinding operation when the web has been severed. It has been the conventional practice to sever the web between the mandrel which has just finished its rewinding operation and the mandrel which is just to start its rewinding operation.
For conventional turret winders rotation of the turret assembly is indexed in a stop and start manner to provide for core loading and log unloading while the mandrels are stationary. Such indexing turret winders are disclosed in the following U.S. Pat. No. 2,769,600 issued Nov. 6, 1956 to Kwitek et al; U.S. Pat. No. 3,179,348 issued Sep. 17, 1962 to Nystrand et al.; U.S. Pat. No. 3,552,670 issued Jun. 12, 1968 to Herman; and U.S. Pat. No. 4,687,153 issued Aug 18, 1987 to McNeil. The McNeil Patent is incorporated herein by reference. Indexing turret assemblies are commercially available on Series 150, 200, and 250 rewinders manufactured by the Paper Converting Machine Company of Green Bay, Wis.
The indexing of the turret assembly is undesirable because of the resulting inertia forces and vibration caused by accelerating and decelerating a rotating turret assembly. Consequently, the indexing turret assembly has been supplanted by a continuously rotating turret assembly as described in U.S. Pat. No. 5,690,297 issued Nov. 25, 1997 to McNeil et al., U.S. Pat. No. 5,667,162 issued Sep. 16, 1997 to McNeil et al., U.S. Pat. No. 5,732,901 issued Mar. 31, 1998 to McNeil et al., U.S. Pat. No. 5,660,350 issued Apr. 26, 1997 to McNeil et al., and U.S. Pat. No. 5,810,282 issued Sep. 22, 1998 to McNeil et al. all of which are incorporated herein by reference. The continuous motion turret assembly provides a means for uninterrupted core loading, core gluing, web rewinding, and log stripping.
Although the continuous rotation turret assembly has resulted in a faster rewinder operating rate, the area which is still not optimized is the web chop-off and transfer procedure. Web chop-off generally requires severing the web at a discrete line of perforation on the web in order to achieve the necessary roll sheet count. To achieve transfer of the web from the one mandrel to another, it is necessary to synchronize the chop-off with transfer of the web to the new mandrel that is about to commence the web winding operation. If the two are not performed simultaneously, control of the web is momentarily lost upon severing the web, leaving an unsupported free end to be urged against an empty core resulting in a wrinkled, uneven web transfer to the empty core and consequently, a poor quality product.
A web chop-off and transfer mechanism typically comprises a chopper roll in combination with a bedroll. The chopper roll and bedroll combination comprises a set of chop-off blades for separating the paper web by breaking the web along one of the lines of perforations. A rewinder of that type where one of the chop-off blades is disposed on the chop-off roll per se, and two on the bedroll, is disclosed in U.S. Pat. No. 4,687,153 which issued Aug. 18, 1987 to McNeil which patent is incorporated herein by reference for the purpose of generally disclosing the operation of the bedroll and chopper roll in providing web transfer.
In that rewinder, the bedroll is a hollow steel cylinder containing components that assist in chop-off and transfer of the web. These include cam actuated blades and transfer pins as well as transfer pads which operate independently from the blades and pins. The two bedroll blades comprise a leading bedroll blade and a trailing blade. The transfer pins are sharpened to a point enabling them to pierce and carry the chopped off web. Approaching chop-off, the bedroll blades are actuated by unlatching a spring loaded mechanism and subsequent contact with a cam in order to lift the web from the surface of the bedroll. Once the blades are fully extended. the web is constrained by contact with a sharp serrated edge of the leading bedroll blade. The blade on the chopper roll enters between the bedroll blades, meshing therebetween. As the meshing occurs, the length of the running web of paper which extends between the tips of the bedroll""s chop-off blades is stretched into a deepening V-shape. The meshing must be adequate to ensure sufficient stretching to induce either tearing or breaking of the web. For more pliable paper running at low web tensions, the meshing operation cannot achieve the desired chop-off resulting in product rolls with incorrect sheet counts or equipment downtime due to a tangled web. Coincident with the blade meshing, the sharp pins which trail the bedroll chop-off blades penetrate the leading edge of the sheet trailing the web break point. During pin penetration the sheet is held against a foam pad mounted to the chopper roll.
In effort to provide a larger chop-off window, an improved web transfer and chop-off assembly was devised providing a means for continuously maintaining the chop-off blades in parallel relationship during roll ending events. Such an assembly is described in U.S. Pat. No. 4,919,351. Issued Apr. 24, 1990 to McNeil and is incorporated herein by reference. The improved transfer and chop-off assembly comprises two side-by-side blades on the chop-off roll and three side-by-side blades along with the transfer pins on the bedroll. The five blades mesh together in a motion parallel to the line between the centers of the bedroll and the chopper roll, allowing deeper blade mesh and a greater stretch while utilizing a wider chop-off window.
For each of the web transfer and chop-off assemblies described, once the web is broken at the perforation, the bedroll pins support the cut end prior to being transferred to the next empty core. During this time, the edge of the cut end is blown in a direction opposite the web transfer, creating a reverse fold. This folded free edge is then transferred to the empty core resulting in a wrinkled, uneven web delivery to the empty core which can effect several revolutions of winding on the core producing a poor quality product and at times, resulting in equipment malfunction.
The present invention provides a web transfer and chop-off assembly in which web transfer to an empty core on the turret assembly is initiated about the same time web chop-off from a roll having completed the web winding cycle occurs. Consequently, control of the web is maintained throughout the web rewinding cycle as the web is transferred from core to core resulting in improved product quality and rewinder reliability.
Performance enhancing fluids are often added to paper webs to improve the properties of the web. For conventional set-ups, the fluid application occurs upstream of the perforator roll generally due to lack of space within the rewinder setup as well as the consequential equipment downtime that would be required to rid the bedroll of the fluids. As a result, the perforator roll becomes coated affecting perforator performance and resulting in significant equipment downtime to clean the perforator roll.
The present invention provides a web transfer and chop-off assembly having improved maintainability while occupying minimal space in the web rewinding set-up by eliminating the need for a bedroll. Such web transfer and chop-off assembly facilitates the installation of a fluid application means within the web rewinder between the perforator roll and the web transfer and chop-off assembly.
A web transfer and chop-off assembly for a web rewinder capable of delivering a web advancing along a path to an empty core faced with glue and supported on a first mandrel of a web winding turret assembly at about the same time the web is severed from a fully wound core supported on a second mandrel in sequence on the turret assembly. The web transfer and chop-off assembly comprises a web transfer assembly juxtaposed to the web path for pressing the web against the empty core and forming a transfer nip therewith during web transfer. A means for accelerating the web is disposed downstream of the transfer nip for producing sufficient tension to break the web from a fully wound core once the delivery of the web to the empty core has been initiated.
In several embodiments of the present invention, the web transfer and chop-off assembly includes a bedroll juxtaposed to the web path. For these embodiments. the web transfer assembly comprises a transfer pad mounted on the periphery of the bedroll. During the rotation of the bedroll, a leading edge of the transfer pad forms a transfer nip with the empty core. The length of the transfer pad is sized to maintain the transfer nip for one full revolution of the empty core and to clear the core during the web winding cycle.
In other embodiments of the present invention, the bedroll has been eliminated and the web transfer assembly comprises a transfer roll having a surface speed that equals the web speed. The transfer roll is rotatably attached to a transfer roll pivot arm. The transfer roll pivot arm rotates the transfer roll about a pivot end from a first position forming a transfer nip with the empty core to a second position withdrawn away from the web, allowing the core to pass and complete the winding cycle.
The web acceleration means of the present invention can comprise two chop-off rolls positioned on opposite sides of the web path downstream of the transfer nip. Each chop-off roll has a surface speed that exceeds the web speed. As the transfer roll forms the transfer nip with the empty core, the two chop-off rolls advance towards one another forming a chop-off nip with the web disposed therebetween. As the web is held at the transfer nip, the chop-off nip accelerates the web creating a tension sufficient to break the web. The two chop-off rolls withdraw from the web allowing the core to pass and complete the winding cycle.